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Date: Tue, 7 Jun 2016 21:16:18 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH -v2] ext4: optimize ext4_should_retry_alloc() to improve ENOSPC performance
On Jun 7, 2016, at 8:46 PM, Theodore Ts'o <tytso@....edu> wrote:
>
> If there are pending blocks to be released after a commit, retrying
> the allocation after a journal commit has no hope of helping. So
> track how many pending deleted blocks there might be, and don't retry
> if there are no pending blocks.
>
> Reported-by: Chao Yu <yuchao0@...wei.com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>
> Oops, ignore the earlier version of this patch. I bobbled the commit
> and merged in part of another change.
>
> fs/ext4/balloc.c | 9 ++++++++-
> fs/ext4/ext4.h | 1 +
> fs/ext4/ext4_jbd2.h | 10 +++++++++-
> fs/ext4/mballoc.c | 12 ++++++++++--
> 4 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index 3020fd7..371ac63 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -603,7 +603,14 @@ int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
> */
> int ext4_should_retry_alloc(struct super_block *sb, int *retries)
> {
> - if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
> + unsigned int pending_blocks;
> +
> + spin_lock(&EXT4_SB(sb)->s_md_lock);
> + pending_blocks = EXT4_SB(sb)->s_mb_free_pending;
> + spin_unlock(&EXT4_SB(sb)->s_md_lock);
Is there a benefit of having a spinlock here? The read of free_pending
should be atomic.
Cheers, Andreas
> +
> + if (pending_blocks == 0 ||
> + !ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
> (*retries)++ > 3 ||
> !EXT4_SB(sb)->s_journal)
> return 0;
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index b84aa1c..96c73e6 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1430,6 +1430,7 @@ struct ext4_sb_info {
> unsigned short *s_mb_offsets;
> unsigned int *s_mb_maxs;
> unsigned int s_group_info_size;
> + unsigned int s_mb_free_pending;
>
> /* tunables */
> unsigned long s_stripe;
> diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
> index 09c1ef3..b1d52c1 100644
> --- a/fs/ext4/ext4_jbd2.h
> +++ b/fs/ext4/ext4_jbd2.h
> @@ -175,6 +175,13 @@ struct ext4_journal_cb_entry {
> * There is no guaranteed calling order of multiple registered callbacks on
> * the same transaction.
> */
> +static inline void _ext4_journal_callback_add(handle_t *handle,
> + struct ext4_journal_cb_entry *jce)
> +{
> + /* Add the jce to transaction's private list */
> + list_add_tail(&jce->jce_list, &handle->h_transaction->t_private_list);
> +}
> +
> static inline void ext4_journal_callback_add(handle_t *handle,
> void (*func)(struct super_block *sb,
> struct ext4_journal_cb_entry *jce,
> @@ -187,10 +194,11 @@ static inline void ext4_journal_callback_add(handle_t *handle,
> /* Add the jce to transaction's private list */
> jce->jce_func = func;
> spin_lock(&sbi->s_md_lock);
> - list_add_tail(&jce->jce_list, &handle->h_transaction->t_private_list);
> + _ext4_journal_callback_add(handle, jce);
> spin_unlock(&sbi->s_md_lock);
> }
>
> +
> /**
> * ext4_journal_callback_del: delete a registered callback
> * @handle: active journal transaction handle on which callback was registered
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index c1ab3ec..77249e1 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2627,6 +2627,7 @@ int ext4_mb_init(struct super_block *sb)
>
> spin_lock_init(&sbi->s_md_lock);
> spin_lock_init(&sbi->s_bal_lock);
> + sbi->s_mb_free_pending = 0;
>
> sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;
> sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;
> @@ -2814,6 +2815,9 @@ static void ext4_free_data_callback(struct super_block *sb,
> /* we expect to find existing buddy because it's pinned */
> BUG_ON(err != 0);
>
> + spin_lock(&EXT4_SB(sb)->s_md_lock);
> + EXT4_SB(sb)->s_mb_free_pending -= entry->efd_count;
> + spin_unlock(&EXT4_SB(sb)->s_md_lock);
>
> db = e4b.bd_info;
> /* there are blocks to put in buddy to make them really free */
> @@ -4583,6 +4587,7 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
> {
> ext4_group_t group = e4b->bd_group;
> ext4_grpblk_t cluster;
> + ext4_grpblk_t clusters = new_entry->efd_count;
> struct ext4_free_data *entry;
> struct ext4_group_info *db = e4b->bd_info;
> struct super_block *sb = e4b->bd_sb;
> @@ -4649,8 +4654,11 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
> }
> }
> /* Add the extent to transaction's private list */
> - ext4_journal_callback_add(handle, ext4_free_data_callback,
> - &new_entry->efd_jce);
> + new_entry->efd_jce.jce_func = ext4_free_data_callback;
> + spin_lock(&sbi->s_md_lock);
> + _ext4_journal_callback_add(handle, &new_entry->efd_jce);
> + sbi->s_mb_free_pending += clusters;
> + spin_unlock(&sbi->s_md_lock);
> return 0;
> }
>
> --
> 2.5.0
>
> --
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Cheers, Andreas
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